Implement chat and markdown views, enhance status bar, and add workflow panel

- Added `chat.rs` for rendering chat messages with timestamps and roles.
- Introduced `markdown.rs` for rendering markdown content with styling.
- Created `status.rs` to display the application status bar with session and message counts.
- Developed `workflow.rs` to show the current workflow status, including tool calls and active jobs.
- Established a `theme.rs` for centralized color management across the UI.
- Updated `mod.rs` to include new modules and manage rendering logic.

src/model/agent_def/builtin.rs

@@ -0,0 +1,66 @@
+use crate::app::subagent::spawn::AgentDefinition;
+
+pub fn builtin_agents() -> Vec<AgentDefinition> {
+    vec![
+        AgentDefinition::new(
+            "coder".to_string(),
+            "coder".to_string(),
+        ).with_system_prompt(
+            "You are a coding agent. Write correct, idiomatic Rust code.".to_string()
+        ).with_allowed_tools(
+            vec![
+                "read".to_string(),
+                "write".to_string(),
+                "edit".to_string(),
+                "bash".to_string(),
+                "grep".to_string(),
+                "glob".to_string(),
+                "git_operator".to_string(),
+            ]
+        ).with_max_steps(25),
+
+        AgentDefinition::new(
+            "reviewer".to_string(),
+            "reviewer".to_string(),
+        ).with_system_prompt(
+            "You are a code reviewer. Focus on correctness, safety, and performance.".to_string()
+        ).with_allowed_tools(
+            vec![
+                "read".to_string(),
+                "grep".to_string(),
+                "glob".to_string(),
+                "recall".to_string(),
+                "remember".to_string(),
+            ]
+        ).with_max_steps(10),
+
+        AgentDefinition::new(
+            "researcher".to_string(),
+            "researcher".to_string(),
+        ).with_system_prompt(
+            "You are a research agent. Search and synthesize information.".to_string()
+        ).with_allowed_tools(
+            vec![
+                "read".to_string(),
+                "grep".to_string(),
+                "glob".to_string(),
+                "search".to_string(),
+                "web_fetch".to_string(),
+            ]
+        ).with_max_steps(15),
+
+        AgentDefinition::new(
+            "planner".to_string(),
+            "planner".to_string(),
+        ).with_system_prompt(
+            "You are a planning agent. Break down tasks into clear steps.".to_string()
+        ).with_allowed_tools(
+            vec![
+                "read".to_string(),
+                "grep".to_string(),
+                "glob".to_string(),
+                "plan".to_string(),
+            ]
+        ).with_max_steps(20),
+    ]
+}